Segmented Bottom Guide for String Elevator Assembly

ABSTRACT

The present invention is directed to a segmented bottom guide for directing the top of a tubular member into and through a bore in the bottom of a tapered bowl so that the tubular member can be engaged by pipe slips. One embodiment of the segmented bottom guide of the present invention comprises a bottom guide retainer having a plurality of chambers for being disposed intermediate the top of a bell guide and the bottom of the tapered bowl. The bottom guide segments are radially received into, and securable in, the retainer to therein and together form a generally conical frustum generally aligned with and intermediate the top of the bell guide and the opening of the tapered bowl.

BACKGROUND

1. Field of the Invention

The present invention is directed to a segmented bottom guide for astring elevator assembly used to handle pipe strings to drill andcomplete a borehole for recovery of oil or gas. Specifically, thepresent invention is directed to a segmented bottom guide for directingthe top of a tubular member into and through a bore so that the tubularmember can be engaged by pipe slips within the string elevator.

2. Background of the Related Art

Wells are drilled to establish a conduit between the surface and atargeted geologic feature such as a hydrocarbon reservoir. Casingstrings are made up and installed in the drilled borehole to preventcollapse, cross-flow from one geologic formation to another, and toisolate the interior of the well from corrosive fluids present in somepenetrated geologic formations. Generally, a pipe string is suspended ina borehole and lengthened by threadedly joining a pipe segment to theproximal end of the pipe string at the rig. The lengthened pipe stringis then lifted to unload the spider that suspends the pipe string, andthe lengthened string is lowered further into the borehole. The spideragain engages and supports the pipe string as additional pipe segmentsare joined to farther lengthen the pipe string.

Special tools exist for positioning a pipe segment to be threadedlyjoined to the proximal end of the suspended pipe string. In one wellknown method, a pipe segment is secured to a lift line that hoists thepipe segment into the derrick to dangle the lower end of the pipesegment near the proximal end of the pipe string. The lower “pin” end ofthe pipe segment is positioned by rig personnel to be received into andbear against the proximal “box” end of the pipe string suspended by thespider in the borehole. A “stabber” is a member of the rig crew thatworks in the derrick. The stabber is secured to the derrick to preventhim from falling as he leans out to manually position the top “box end”of the pipe segment to align it with the pipe string. A power tong maybe used to grip and rotate the pipe segment about its axis to make upthe threaded connection between the lower “pin end” of the pipe segmentand the proximal box end of the pipe string to lengthen the pipe string.The stabber then aligns the top box end of the now-connected pipesegment into the bell guide of the string elevator so that the box endof die pipe segment can be directed into the gripping portion of thestring elevator as the string elevator is lowered over the end of thepipe segment. Once the string elevator is lowered enough to engage andgrip the upper end of the pipe segment (which is now the new proximalend of the lengthened pipe string), the string elevator lifts the entirepipe string to unload the spider, and then it lowers the pipe string toinstall the lengthened pipe string further into the borehole.

When the string elevator nears the spider, the spider may reengage andsupport the pipe string to strategically position the new proximal endof the now-lengthened pipe string above the spider to receive and coupleto a new pipe segment. This method of forming and installing a pipestring in a borehole is repeated until the pipe string reaches itsdesired length.

The string elevator used in the method described above is adapted toreceive the proximal end of a lengthened pipe string from below, and tobe lowered over the end of the proximal end of the pipe string as it ispositioned by the stabber for being received into the elevator. Afterthe proximal end of the pipe string is received into the tapered bowl,it may be releasably gripped using a set of slips that have been movedupwardly and radially outwardly from the center of the tapered bowl toreceive the pipe string, and that can be engaged by moving downwardlyand radially inwardly within the tapered bowl to engage and grip thepipe string. The proximal end of the pipe string must generally becarefully positioned by the stabber to ensure that it enters the stringelevator from beneath as the string elevator is lowered using adrawworks. After the pipe segment is threadedly connected to the exposedproximal end of a pipe string, the pipe string is lengthened, and thenew proximal end of the pipe string is positioned high above the rigfloor. The proximal end is then guided through the opening in the bottomof the tapered bowl and into the tapered bowl so that the lengthenedpipe string can be gripped and then lifted up to unload the spider.

The insertion of the proximal end of the lengthened pipe string into theopening in the bottom of the tapered bowl has to be done at a positionfar above die rig floor where it is impractical for rig personnel tophysically guide tie proximal end of the pipe string into the opening inthe bottom of the tapered bowl. For this reason, the string elevator isgenerally provided with structures adapted for guiding the proximal endof the lengthened pipe string into and through the opening so that theproximal end of the pipe string can be gripped by the slips within thetapered bowl. A bell guide is a generally hollow interior conicalfrustum for receiving and guiding the top end of the lengthened pipestring toward the opening in the tapered bowl of the string elevator.

The bottom guide is a second structure for cooperating with the bellguide in guiding the top end of the pipe string into the opening of thetapered bowl. The bottom guide is secured between the bell guide and theopening in the bottom of the tapered bowl to receive the top end of thepipe string after it leaves the bell guide and to further direct it tothe opening. Since most string elevators can be “dressed” or modifiedusing inserts, spacers and sleeves to grip and lift a range of pipediameters, the diameter of the opening in the bottom of the tapered bowlmay vary depending on the diameter of the pipe string being made tip andrun into the borehole. For this reason, the bottom guide may bereplaceable to enable the use of an appropriately-sized bottom guide forreceiving the top end of the pipe string from the top of the bell guideand guiding it to the opening in the tapered bowl. The bottom guide musthave the appropriate size and taper for guiding the received top end ofthe pipe string to the opening.

However, depending on its capacity, the string elevator may weigh up to15,000 pounds or more. Similarly, the slips, the bell guide and thebottom guide each may weigh hundreds of pounds. Replacing, the heavybottom guide can be difficult and time consuming, not only because ofthe weight, but also because the bottom guide is generally positionedbetween the bell guide and the tapered bowl, and access to the bottomguide often requires removing the bell guide and removing fasteners fromunderneath the heavy tapered bowl. Once removed from the tapered bowl,the bottom guide may be very heavy and difficult to handle. The bottomguide may require removal of other heavy components, such as the bellguide, to provide access to the bottom guide. For example, onecommercially available string elevator requires removal of the heavyslips to replace the bottom guide. Other string elevators require thatthe string elevator be suspended for replacing the bottom guide, andpersonnel replacing the bottom guide must work with their handsunderneath the suspended string elevator, thereby exposing personnel topotential danger or, at the very least, a difficult working position.

What is needed is a string elevator assembly that provides easier accessto the bottom guide so that the bottom guide profile can be adapted toguide the top end of a pipe string from the top of a bell guide to theopening in the bottom of the tapered bowl. What is needed is a stringelevator assembly that facilitates the replacement of the bottom guidewithout exposing rig personnel to unnecessary danger or difficultworking positions. What is needed is a more versatile string elevatorassembly that includes a bottom guide that can be safely replaced toaccommodate a range of pipe diameters.

SUMMARY

The present invention satisfied some or all of the above-stated needs,and others. The present invention comprises a string elevator assemblyhaving a bottom guide intermediate a bell guide and a tapered bowl thatis segmented to facilitate radial installation mid radial removal of thebottom guide segments to form and remove an interior conical frustum forguiding the end of a pipe into the tapered bowl of a string elevator.The bottom guide segments are adapted for being, captured within aretainer that couples the bell guide to the tapered bowl of the stringelevator. The present invention comprises a segmented bottom guide foruse in aligning the top end of a pipe for being received into an openingwithin the tapered bowl of a vertically positionable string elevator.The bottom guide of the present invention comprises a retainer thatcomprises a plurality of chambers therein, each for receiving andretaining a bottom guide segment. Each bottom guide segment comprises acurved face that forms, together with the curved faces of the otherbottom guide segments, a portion of a conical frustum to funnel andguide the top end of a pipe string from the top of a bell guide to theopening in the bottom of a tapered bowl in which the pipe string is tobe gripped. The conical frustum formed by the curved faces of theretained bottom guide segments form a generally convergent interiorsurface to contact and guide the top end of the pipe string as thestring elevator assembly is lowered downwardly to receive and direct apipe string into the tapered bowl. Once the pipe string has beensuccessfully directed to the bore of the tapered bowl, the slipsreceived within the tapered bowl are closed to grip and support the pipestring.

So that the manner in which the above recited features of tile presentinvention can be understood in detail a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings.However, that the appended drawings illustrate only typical embodimentsof this invention and are therefore not to be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of one embodiment of the stringelevator assembly of the present invention.

FIG. 2 is an assembled perspective view of tie string elevator assemblyof FIG. 1.

FIG. 3 is a bottom view of the string elevator assembly of FIG. 2,further having a circle indicating the position of the end of a pipestring received into the bell guide and corresponding to the position ofthe pipe string in FIG. 6.

FIG. 4 is the bottom view of FIG. 3 illustrating the movement of the endof the pipe string within the bell guide and to the interface betweenthe bell guide and the bottom guide that surrounds the opening in thebottom of the tapered bowl. The circle indicating the position of theend of the pipe string corresponds to the position of the pipe string inFIG. 7.

FIG. 5 is the bottom view of FIG. 4 illustrating further movement of theend of the pipe string as guided by the bottom guide to a positionaligned with the opening in the bottom of the tapered bowl. The circleindicating the position of the end of the pipe string corresponds to theposition of the pipe string in FIG. 8.

FIG. 6 is the elevation view corresponding to FIG. 3 illustrating theposition of the pipe string received within the bell guide for beingguided into a bottom guide surrounding an opening in the bottom of thetapered bowl.

FIG. 7 is the elevation view corresponding to FIG. 4 illustrating theposition of the pipe string after movement of the string elevatorassembly downwardly to further receive the pipe string.

FIG. 8 is the elevation view corresponding to FIG. 5 illustrating theposition of the pipe string after further movement of the stringelevator assembly downwardly to further receive the pipe string.

FIG. 9 is the elevation view of FIG. 8 illustrating the position of thepipe string after further movement of the string elevator assemblydownwardly to insert the end of the pipe string into the tapered bowlwhere it is gripped by engagement of the slips.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is one embodiment of a string elevator assembly 10 of the presentinvention having a tapered bowl 12, a plurality of slips 16 for movementradially inwardly and downwardly within the tapered bowl 12 to grip andsupport a pipe string (not shown in FIG. 1) received into the stringelevator along its axis 80 and introduced through the bottom 21 of abell guide 20. The string elevator assembly 10 is supportable above arig floor by bails (not shown in FIG. 1) that may engage and supportlift ears 14. The bails are not shown in FIG. 1 to reveal the stringelevators assembly 10 in more detail.

The slips 16 are movable between an engaged position and a disengagedposition (shown in FIG. 1) using a timing ring 18. The timing ring 18may be actuated downwardly by retraction of rods 19 into the wall of thetapered bowl 12 to engage the slips 16 against the exterior surface of apipe string 88 (not shown in FIG. 1). Subsequently, the string elevatorassembly 10 may be disengaged from the pipe string 88 by extending rods19 upwardly from the wall of the tapered bowl 12 to disengage the slips16 from the pipe string (not shown). The rods 19 may be hydraulically,pneumatically or mechanically actuated to elevate and thereby disengagetie slips 16 from the pipe string, and may be hydraulically,pneumatically, mechanically or gravitationally actuated to lower andthereby engage the slips 16 with the pipe string. FIG. 9 illustrates theposition of the timing ring 18, the rod 19 and the slips 16 when in theengaged position, and the direction 19′ of movement of the timing ring18 to engage the slips with the pipe string 88.

Returning again to FIG. 1, the string elevator assembly 10 comprises aretainer 30 that may be coupled at its bottom 30 b to the bell guide 20and at its top 30 a to the tapered bowl 12, or to an intermediate memberconnected thereto. The retainer 30 comprises a plurality of generallyradially extending supports 32 disposed intermediate the top 30 a andthe bottom 30 b of the retainer 30 to provide support for the bell guide20 when it is coupled to the tapered bowl 12. A plurality of chambers 36are formed between the supports 32, each for receiving and retaining abottom guide segment 40 in a generally assembled arrangement with theother bottom guide segments. Each bottom guide segment 40 comprises acurved face 46 intermediate opposed notched ends 42. The curved faces 46of the bottom guide segments 40, when the bottom guide segments 40 areretained within the chambers 36 of the retainer 30, together form agenerally continuous section of the interior of a conical frustum thathas a bottom disposed toward the top of the bell guide 20 and a lopdisposed toward the tapered bowl 12, and having convergence in thedirection of the top so as to funnel and guide the end of a pipereceived within the interior 22 of the bell guide 20 toward an opening(not shown in FIG. 1) in the bottom of the tapered bowl 12.

FIG. 2 illustrates the configuration of the string elevator assembly 10of FIG. 1 after it is assembled for use in forming and lengthening apipe string. The bottom guide segments 40 are retained within thechambers 36 of the retainer 30 using curved retainer plates 50 that aresecurable to the retainer 30 using bolts 52 that are threadedlyreceivable into corresponding threaded holes 54 the supports 32. Eachcurved retainer plate 50 comprises a pair of generally aligned aperturesfor receiving bolts 52, and each bottom guide segment 40 is securablewithin a chamber 36 by the adjacent ends of each of the adjacent curvedretainer plates 50. It should be understood that the bottom guidesegments 40 are securable within the chambers 36 using a variety offasteners and retainers.

The notched ends 42 of each bottom guide segment 40 may be shaped orcontoured to cooperate with a corresponding shape or contour of thesupports 32 located on either side of the chamber 36 of the retainer 30in which the bottom guide segment is to be radially received. Thesecorresponding shapes of the notched ends 42 and the supports 32 mayassist in positioning the bottom guide segment 40 within the chamber 36.Similarly, the top 42 and the bottom 43 of each bottom guide segment 40may be shaped or contoured to cooperate with a corresponding shape orcontour within the retainer 30 in which the bottom guide segment 40 isreceived and retained. In FIG. 2, the top 42 and the bottom 43 of eachbottom guide segment 40 are smooth to facilitate simple slidinginsertion and removal of each bottom guide segment 40 from a chamber 36of the retainer 30.

FIGS. 3-5 are bottom views of the string elevator assembly 10 of thepresent invention corresponding to the elevation views of FIGS. 6-8.Each bottom view of FIGS. 3-5 shows the bell guide 20 having a generallyinterior conical frustum 22 and the generally axially aligned conicalfrustum formed by the faces 46 of the bottom guide segments 40 that aresecured in an arrangement within the chambers 36 of the retainer 30 (notvisible in FIGS. 3-5, see FIGS. 6-8). FIGS. 3-5 all show an arrangementof slips 16 within the tapered bowl 12 (not shown in FIGS. 3-5, seeFIGS. 6-8). FIGS. 3-5 further show the generally axially aligned and thegenerally conically aligned interior surfaces of two separate conicalfrustums, one being the interior conical frustum 22 of the bell guide20, and the other being the interior conical frustum formed by thecurved faces 46 of the bottom guide segments 40 when the bottom guidesegments 40 are retained within the chambers 36 of the retainer 30. Thetwo conical frustums may be positioned one adjacent to the other asshown in FIGS. 3-5 to together form a single conical frustum, or theymay be positioned to form two adjacent conical frustums, each having aslope different from the other, but generally converging in the samedirection to guide the end of a pipe received therein to an opening 21in the bottom of the tapered bowl 12 (see FIGS. 6-8).

FIG. 3 is a bottom view of the string elevator assembly 10 thatcorresponds to the elevation view of FIG. 6, and these figures togetherillustrate the position of the top end 87 of a pipe string 88 receivedwithin the bell guide 20 by lowering the string elevator assembly 10downwardly to receive the pipe string 88 within the bell guide 20. Thepipe string 88 is shown in FIG. 6 to be generally misaligned with theopening 21 and the cylinder defined by the slips 16 movably receivedwithin the tapered bowl 12 (not shown in FIG. 3). The opening 21 isgenerally aligned with the axis 80 of the tapered bowl 12. As the stringelevator assembly 10 is lowered to receive the top end 87 of the pipestring 88 into the bell guide 20. The contact point 87A shows theinitial point of contact between the interior conical frustum 22 of thebell guide 20 and the top end 87 of the pipe string 88 as the top end 87slides generally upwardly and in the convergent direction of the conicalfrustum 22 toward the curved faces 46 of the bottom guide segments 40 tothe position shown in FIG. 4.

FIG. 4 is a bottom view of the string elevator assembly 10 thatcorresponds to the elevation view of FIG. 7, and these togetherillustrate the position of the top end 87 of a pipe string 88 receivedwithin the bell guide 20 alter it slides upwardly along the interiorsurface of the conical frustum 22 of the bell, guide 20 from itsposition shown in FIGS. 3 and 6. The contact point 87A shown in FIG. 4is shown to be generally contacting the interface between the curvedfaces 46 of the bottom guide segments 40 and the top of the conicalfrustum 22 of tile bell guide 20. From this position, the adjacentconical frustum formed by the curved faces 46 of the bottom guidesegments 40 will continue to guide the top end 87 of the pipe string 88toward its position shown in the bottom view of FIG. 5 and the elevationview of FIG. 8 aligned with the opening 21 and with the cylinder definedby the slips 16 that are movably received within the tapered bowl 12.

FIG. 5 is a bottom view that corresponds to the elevation view of FIG.8, and these together illustrate the position of the top end 87 of thepipe string 88 after the string elevator assembly 10 is lowered furtherfrom its position of FIG. 4, and after the pipe string 88 is furtherreceived within the bell guide 20 and the arrangement of the curvedfaces 46 of the bottom guide segments. The pipe string 88 is shown to begenerally aligned with the axis of the bell guide 20 and the conicalfrustum formed by the arrangement of the bottom guide segments 40. Thepipe string 88 is also aligned with the opening 21 and the cylinderdefined by the slips 16 within the tapered bowl 12. The alignedcondition of the pipe string 88 with the axis 80 of the tapered bowl 12and the bore 21 defined by the slips 16 received therein permits thestring elevator assembly 10 to be lowered further, and for the pipestring 88 to be inserted within the bore 21 by continued downwardmovement of the string elevator assembly 10 and then positioned to begripped by movement of the slips 16 radially downwardly and inwardlywithin the tapered bowl 12, as shown in FIG. 9.

FIG. 9 is an elevation view of the string elevator assembly 10 of FIG. 8after the string elevator assembly 10 is lowered further from itsposition of FIG. 8 to insert the top end 87 of the pipe string 88through the opening 21 in the bottom of the tapered bowl 12.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of tile invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A string elevator assembly vertically positionable using a drawworksand comprising: a tapered bowl for receiving and cooperating with a setof slips to engage and grip a pipe to be supported within the stringelevator, the tapered bore terminating at its bottom at an opening; abell guide having an interior generally shaped like a section of aconical frustum and having a generally circular, downwardly disposedbottom for receiving the end of a pipe to be gripped within the taperedbowl and a generally circular, upwardly disposed top, the bell guidesuspended generally aligned with and underneath the tapered bowl; abottom guide retainer having a plurality of chambers, and disposedintermediate the top of the bell guide and the bottom of the taperedbowl; and a plurality bottom guide segments, each having a curved face,each segment adapted for being received mid secured within the bottomguide frame; wherein the curved faces of the bottom guide segments, whenreceived within the retainer, together generally form a section of aconical frustum aligned with and intermediate the top of the bell guideand the opening of the tapered bowl.
 2. The string elevator assembly ofclaim 1 wherein the bottom guide retainer further comprises a pluralityof supports defining the chambers therebetween.
 3. The string elevatorassembly of claim 2 wherein the supports extend generally radially froma bore within the retainer.
 4. The string elevator assembly of claim 3wherein the supports are intermediate a top mount and a bottom mount forcoupling the retainer to a tapered bowl and a bell guide, respectively.5. The string elevator assembly of claim 4 wherein the top mount isintegral with the tapered bowl.
 6. The string elevator assembly of claim4 wherein the bottom mount is integral with the bell guide.
 7. Thestring elevator assembly of claim 3 wherein the bottom guide retainer isadapted for receiving, in a generally radial direction, a bottom guidesegment within each chamber of the retainer.
 8. The string elevatorassembly of claim 1 wherein the interior of the bell guide is generallyshaped like a first section of a conical frustum and the curved faces ofthe bottom guide segments, when retained within the retainer, togetherform a second section of the same conical frustum.
 9. The stringelevator assembly of claim 1 wherein the interior of the bell guide isgenerally shaped like a conical frustum and the curved faces of thebottom guide segments, when retained within the retainer, together forma section of a different conical frustum.
 10. An assembly comprising astring elevator and a bell guide supported axially underneath the stringelevator, the assembly having a plurality of chambers intermediate thestring elevator and the bell guide, each for radially receiving at leastone bottom guide segment having a curved face.
 11. The assembly of claim10 further comprising a plurality of bottom guide segments; each forbeing radially received, retained and released from a chamber.
 12. Theassembly of claim 11 wherein each bottom guide segment comprises acurved face of a common radius with the others for forming a portion ofthe interior of a section of a conical frustum.
 13. The assembly ofclaim 12 wherein each chamber is shaped to receive the curved face firstupon receiving the bottom guide segment.
 14. The assembly of claim 13wherein each bottom guide segment is releasably secured within a chamberby one or more retainers.
 15. The assembly of claim 13 wherein eachbottom guide segment is releasably securable in a chamber by a retainerselected from the group comprising a bolt, a screw, a spring-loaded balland corresponding detent, a pin and a rotatable lever.
 16. The assemblyof claim 10 wherein the bell guide is releasably secured underneath thestring elevator by a plurality of radially extending supports defining aplurality of chambers there between.
 17. The assembly of claim 10wherein the axis of the conical frustum formed by the curved faces ofthe retained bottom guide segments is generally aligned with the axis ofa cylinder formed by the slips of the string elevator.
 18. The assemblyof claim 11 wherein the interior of the bell guide forms a section of afirst conical frustum and the curved faces of the bottom guide segments,when retained within the retainer, together form a section of a secondconical frustum.
 19. The assembly of claim 10 further comprising atiming ring coupled to a plurality of slips movable between an engagedposition and a disengaged position within a tapered bowl.
 20. A bottomguide assembly comprising a bore, a top side coupled to a stringelevator and a bottom side for securing to a bell guide, a plurality ofsupports intermediate the top side and the bottom side, each supportextending from radially the bore to form a plurality of chambers therebetween.
 21. The bottom guide assembly of claim 20 further comprising aplurality of bottom guide segments, each shaped for being releasablysecured with a chamber and together form the interior of a conicalfrustum central to the chambers.